Peg Gear Clock The History of Longitude Navigation by Marine Chronometer and Astronomical Methods

Since ancient times, navigation across open oceans was unreliable and dangerous, until latitude and longitude measurements were made directly from the moving ship. Coordinates of latitude and longitude are necessary for safe navigation on the ocean. Latitude is simply the angle north or south of the equator as measured using the center of the earth as the vertex. Latitude is quite easily determined from altitude measurements of the sun and/or stars using a sextant; in the northern hemisphere, the north star (Polaris) provides the observer's latitude directly. But longitude remained unknown for many centuries, even after the Vikings and Columbus sailed across the Atlantic ocean... continue reading article All Images and Content, Copyright H. and S. Houtman January 2010